How to be an Otter Spotter

PUBLISHED: 12:15 24 April 2008 | UPDATED: 15:07 20 February 2013

Running Otter by Kate Stokes

Cornwall can proudly boast it is a stronghold for otters, and while they are notoriously elusive, they do leave some wonderful (and aromatic) signs. In this May issue, The Cornwall Wildlife trust teaches us how to become an otter spotter

Cornwall can proudly boast it is a stronghold for otters, and while they are notoriously elusive, they do leave some wonderful (and aromatic) signs. Kate Stokes explains how to become an otter spotter

There is only one kind of otter found in the British Isles - the river otter (Lutra lutra). Our otter can make use of the sea, but fresh water is absolutely essential. Otters can be found on any kind of waterway or wetland including rivers, streams and canals, lakes and ponds, reedbeds, wet woodland and moorland. The South-west is latticed with a network of such habitats and is superb otter country. In recognition of this, the River Camel in North Cornwall has been designated as a Special Area of Conservation primarily for otters - giving Cornish otters particular importance.

Otters are carnivores and belong to the weasel family (Mustelidae), which includes badgers, ferrets, mink, polecats and stoats. Mustelids typically have long, thin bodies, short legs and musky scent glands under their tails, and they move in a graceful, undulating fashion. The otter is a semi-aquatic mammal, which spends much of its time in the water. Consequently it is most frequently confused with its semi-aquatic cousin the American mink, introduced to Britain in the 1920s.

However, the otter is nearly twice the size of a mink and over one metre long, and is a milk-chocolate-brown colour with a creamy chest. The mink, on the other hand, is plain-chocolate-brown to black, with thick glossy fur, often with a small white patch on its chin. The otter is better adapted for swimming and has a powerful, sinuous body with a long tapering tail used for propulsion. Its feet are quite large and webbed for extra power. The otter swims low in the water, is elusive and can be hard to detect. By contrast, mink are more buoyant, bold and nosey and, therefore, easier to spot.

While it is difficult to see otters, they do leave some signs, the best of which is their spraints - a lovely name for droppings, but which also have a lovely smell! Spraint smells sweet - a bit like jasmine tea with a hint of fish oil. Up to 95% of an otter's diet is fish, which it detects by using its long, sensitive whiskers (vibrissae) in dark, murky waters. Careful analysis of spraint can reveal exactly what an otter has eaten, and it is usually full of distinctive fish bones and scales. Eels are a favourite food, as are frogs. Otters feast on frogs that are distracted by courting, and their spraints are subsequently full of flat, hollow frog bones that are easy to spot as they are white.

Otters will also make use of coastal waters, taking sea fish and crabs. In Cornwall there are a few records of otters consuming mammals or birds, which is a testament to our clean waters. In contrast, mink droppings, called scats, smell revolting when fresh, and as mink have a more diverse diet, their scats contain feathers, fur and mammal bones.

Otters are very territorial and leave spraint to mark their territory. These are deposited in prominent places, especially at the confluence of rivers and streams, under bridges, on islands, on rocks in the middle or at the edge of a water course, or on boulders where fresh water meets the sea.

A male (or dog) otter's home range can be up to 40km (25 miles), and the size of their territory will depend on the quality of the wetland habitat; coastal territories may be a lot richer and, therefore, smaller. Otters live solitary lives most of the time, except when courting or rearing cubs. Mating takes place on land or in water. They can breed at any time of the year although most births occur in spring or late autumn and they usually have one cub or twins. Cubs stay with their mother for about a year, with the dog playing no part in rearing the young.

While spraint and other signs such as tracks tell us where the otters are, more specific information such as sex, breeding condition, health status and age come from post-mortem work, and this is provided by otter road casualties. Otter corpses are reported by members of the public to Cornwall Wildlife Trust, who see to their collection as a priority. Up until 2008 the post mortems were carried out at the Wildlife Veterinary Investigation Centre at Chacewater, near Truro, but are now conducted at Cardiff University. If the corpse is that of a lactating female, a cub search may be organised. There are more otter road deaths in Cornwall and Devon than anywhere else in England, but this is both a bad and a good news story, simply reflecting the fact that we have more otters down here to get run over.

Despite the county being a stronghold for the otter it is still difficult to see them. They are secretive and clever. For the determined otter spotter you will need a lot of patience and some luck. Dusk and dawn are good times to look out for them, and also during or after rainfall. Perhaps human smell is masked by the rain and perhaps also the otter has to concentrate harder when hunting in swollen, murky rivers. Fishermen frequently see otters as they silently wait for long periods along river banks. However, you may get lucky and see an otter when you are not expecting to.

Over the last ten years in Cornwall the otter hotspots have included St Ives, Truro, St Austell and Bude. The River Camel also provides good opportunities. Cornwall has a growing band of volunteer otter spotters. If you see an otter, dead or alive, contact the Cornwall Wildlife Trust as this is important information that can be added to a long-term monitoring programme for this rare but recovering and charismatic species.

For further information on how to become a volunteer for otter spotting contact Cornwall Wildlife Trust on (01872 240777 ext 214.